Electric incandescent lamp



J. RUNDERS ELECTRIC INCANDESCENT LAMP Nov. 4, 1952 2 SHEETSSHEET 1 FiledApril 11, 1950 INVENTOR J-OHANNES RIJNDERS AGENT Nov. 4, 1952 J.RIJNDERS ELECTRIC INCANDEISCENT LAMP Filed April 11, 1 950 JOHANNES R188% Patented Nov. 4, 1952 UNITED STAT ES PAT EN T" OFFICE ELECTRIC.INCANDESCENT' LAMP Johannes Rijnders; Eindhoven; Netherlands assignorto' Hartford National Bank and Trust Company, Hartford, Conn., astrustee Application April 11, 1950,-Serial l\lo.-1 55 ,238

Inthe Netherlands April13p1949 This invention relatesto electricincandescent 1amps,. particularly for. use in vehicle lighting, whichcomprise .at least onefilament and a cupshaped screen, andlin which thefilament" is located between at least two lateral edges of the screen.

Such lamps are arranged in a spotlightv or headlight in such manner.thatthe filament extends substantially in the optical axis of'theoptical system of the spotlight. This optical system usually consistsof- 'a reflector shapedin the form of a parab'oloid of revolution. Thescreen serves to prevent light from-falling on one side of. thereflector, thusobtainin'g the so-called dipped? lighting, when the.light is directed solely below the horizontal plane extending throughthe lamp. Thescreengenerallyconsists of a metal. cup-shaped hoodgfor.example, of nickel, arranged in close proximity to the filament in thelamp. The. screen is, generally of a small size, in order to intercept aminimum quantity of light from a secondl'filament generally provided inthe lamp, calledlthe main filament herein, which produces..the.undippedor. normal beam. The firstrfilament is calledthe dipping filamentherein. If only the latter is-provided in the lamp, there .isgenerallyino objection to makingthe screen considerably larger and applying it,for exampleinthe formv of'a mirror or a layer of lacquer, on to thelampbulb.

If a screen isiarranged transversely of the optical axis of thelightbeamand atawdi'stancaior example m., in. front oisthela'mpaa patch of lightviz. the beam pattern is.projected.thereon. By operating alternativelyone filament. or the other, a so-called main and la .dipped? beam isproduced respectively, thebeam patterns of 'most lamps beingsubstantially circular,.semi-circular or approximately elliiaticaL. Itis to be noted that in the present case referenceismade only toco-operation of the lamp with. an optical system havingrotationalsymmetry, suchlasthe aforesaid refiectoninorder to make theproperties of the lamp better understood. Consequently no reference ismade. to the .use. ofimeans, such-as ribbed refiectorsof' front glasses,for directing the light.

The well-known lamps produce a' dipped beam pattern having. acomparatively large radius, 1. e. that a greatly diffused beam isproduced ina ,verticaldownward direction, a large part of the light fluxproduced'bythe dipping? filament being projected Ontotheroad at acomparatively short distance infront of thevehicle. As. a resultof thisillumination thesensitiveness of a drivers" eyes-"'adiiists"itself tothisbri'ght illuminationoccupying a considerable part of his field ofview, so that he is handicapped inobserving' more remoteobstaclesfi Theinventionhas forits obje'c't inter aliato mitigate this limitationandto" provide a construction of lamp which gives-fdipped lighting andpermits'th'e light 't'obe radiated in thfo'rm of a beam,whichisccmp'aratively litt l-e 'difi iised, and at aconsiderabledistancein iron-tot the vehicle:

According to the-invention} the filament is located-between atleasttwo-side walls of the screen; is'V-shaped"and"extends in aplane which isparallel to or-coincides'with the plane through the edges of the-screen:Iiia" normalheador spot-light comprisin'gf'a reflector in the-former aparaboloid of revolution, this lamp should be arrangedsuch' that the"plane of the" filament extends horizontally" slightlyabove the axis ofthe reflector'and 'the top of the v shaped filament is near the focus'oftherefl'ectbr, the limbs ofthev extending on-eitherside-above the axis.This resultsiir a beam pattern; the sectional area" of whichisapproximately" se'mi elliptical with a' small elevation: the highestluminous intensity being just below'the upper boundary: It is thisluminous intensity whicnenab'les obstacles to bemade-visible at'agreat-'di'stancein front of the vehicle.

It is pointed out that v -snaped filaments are frequentlyused" as mainfilament lamps for vehicle lighting: Thisshape has' al'sobeenusedfor'the dipping filament but, fbfthis purpose, not" combined with" ascreen, andin a: difierent position (British patentspecification440g956aiid American" patent specification" 2,214,472) Thefilamentsarranged betweenthe edgesof 'a screen were"generallyre'ctilinear' (for example" British patent specifications"442;939and "393386) v Inorder that theinventionmaybe readily carriedinto efiect', a" number of "examples will now be described more" fully"with reference to the accompanyingdrawings, in which:

Figs". 1 and' l. are diagrammatical vertical sectionsiof headlightscomprising a" lampiofkno'wn type'and of avarlant thereof respectively;

Figs." 2 and 5""areplan'viewsof these lamps;

Figs: Band "(ishdwth'e beam'pa'tterns produced by $11 lamps?" Fig. '7 isa diagrammatical lioi'izoiital-sectionof a lamp according to theinvention without screen and dipping filament;

Figs 8 and l0 show diftrentforms of a 'dipping filament according totheinvention Fig. 11 is a diagrammatical vertical section of a headlightcomprising a lamp according to the invention;

Fig. 12 is a plan view of the lamp according to Fig. 11;

Fig. 13 shows the beam pattern of the lamp according to Fig. 11;

Fig. 14 is a diagram of the light distribution produced by a known lampand by a lamp according to the invention;

Fig. 15 shows the beam pattern of an incandescent lamp comprising anasymmetrical V-shaped filament;

Fig. 16 is a plan view and Fig. 1'7 a side view of an incandescent lampand a screen of a lamp according to the invention;

Figs. 18 to 20 are a plan view and two side views respectively of thefilament body and the screen of a lamp in a modified embodiment and Fig.21 is a plan view of a filament and screen in a third embodiment.

The lamp shown in Figs. 1 and 2 comprises a bulb l, a main filament 2, adipping filament 3, a screen 4, a cap 5 and a few parts (not shown) suchas supporting wires for the filaments and the screen, and the pinch inwhich these wires are secured. The lamp is arranged in a reflector 6having the shape of a paraboloid of revolution. The lamp is adjusted ina manner such that the main filament 2 is located at the focus F.

A light ray I from the main filament 2 will extend, subsequent toreflection by the reflector E, parallel to the optical axis 8 of thisreflector. A ray 9 from that part of the clipping filament 3 which isnearest to the focus F, extends, subsequent to reflection, in a slightlyslanting downward direction, whilst a ray in from that end of theclipping filament body which is most remote from the focus F has asteeper slope.

In the present case, the filament 3 is located between the edges H, l2and 13 of the screen 4 (Fig. 2). These edges extend approximately in oneplane with the filament. Only the edge 14 does not extend in the planebut extends in a higher plane, in order to prevent light directly fromthe filament 3 from shining on approaching trafiic. These edges form theupper boundary of the side walls.

Where in the present specification reference is made to a filamentextending in a plane, it should be considered that a filament naturallyhas certain dimensions and cannot coincide mathematically with a plane,so that such reference is to be taken colloquially.

The beam pattern produced by this known lamp consists of the imagesformed by various parts of the reflector of the filament. These imagesmay be shown separately by shielding off the remaining reflector parts.Thus, vertically below the point of intersection B of the optical axis 8with the screen, a series of images 15 is formed by the reflector partslocated in or near the vertical plane through the optical axis 8. Theseries of images 16 and I! through the said axis on either side of thelamp (i. e. under or above the plane of the drawing in Fig. 1). Thereflector parts located between these limits form series of images, forexample, the series 18 and I9. The whole light falls, however, below thehorizontal plane through 0, owing to the presence of the screen 4 whichprevents light from falling on the lower reflector part and owing to theposition of the filament 3 in front of the focus F and slightly abovethe axis 8.

From the foregoing it will be seen that the diameter D of the dippingbeam is substantially proportional to the length of the dipping filamentL (Figs. 3 and 1). Due to the comparatively great length of such afilament, the beam has such a diameter that a great part of the lightflux is projected on to the road at a short distance in front of thevehicle.

If the dipping filament is arranged transversely of the axis at thefocus F, as shown in Figs. 4 and 5, this would yield the beam patternshown in Fig. 6. The reflector parts located in or near the verticalplane through the axis 3 form elongated, horizontal images 20 of thefilament 3; reflector parts located in or near the horizontal planethrough the axis 8 produce comparatively short, compact images 2! nearthe axis passage 0. The intermediate reflector parts, consequentlylocated in oblique planes through the axis, produce a number of obliqueimages 22 located in part above the horizontal plane through the axis.This proves that, in spite of the presence of the screen 4, a puredipped lighting is not produced. Furthermore it is obvious that thiseffect is the more troublesome, according as the filament 3 (Fig. 5) islonger and protrudes more on either side of the axis.

On the other hand it appears from Fig. 1 that the reflected light frompart of the filament is more reflected downward as this part is morelocated in front of the focus (see for example light rays I, 9 and I0 inFig. 1). The oblique images 22 (Fig. 6) can thus be prevented fromextending above the horizontal plane by placing the filament body 3 atan adequate distance in front of the focus.

In this event, however, the images 26 also descend, so that an undulystrong front illumination is produced.

The invention is based on the recognition that the optimum beam patternis produced, if the filament is kept within the limits of an angle 23(Fig. 7), the apex of which is at the focus F and which extends on bothsides of the axis 8. The ideal shape of the filament would consequentlybe a triangular luminous surface. Although such a filament is feasible,for example, in the form of a tungsten plate which is heated to a hightemperature by the passage of current or by gas discharge, a suificientapproximation is obtained in practice with the use of a normal coiledfilament which is bent with two limbs forming the said angle 23, asshown in Fig. 8. If the angle formed by one of the limits of the angleand the axis 9 be 18 (Fig. '7), it is found from experiments withdifferent conventional reflectors that this angle may be between 60 and15 (Figs. 9 and 10). In a very suitable form, a=30 (Fig. 8). TheV-shaped filament will usually be arranged symmetrically with respect tothe axis of the lamp, but sometimes a nonsymmetrical arrangement may beadvantageous, for example to cause more light to shine on one road halfthan on the other road half.

Figs. 11 and 12 show diagrammatically the use of such a lamp in areflector. The reference numerals correspond to those used in Figs. 1,2, 4 and 5.

Fig. 13 shows the beam pattern produced by several parts of thereflector. The reflector parts located in or near the vertical planethrough the axis produce a series of images 24. They are magnifiedimages of the V-shaped filament. The reflector parts located in or nearthe horizontal plane through the axis are facing, as it a civpac 5.were; the side of the gv shapeda filament-and coni sequently do notreproduce Vj 'b itarectangle so that two series of images 25are'produced to the left and to the right of the axis 0, of whichonlyone series is-shown. -The intermediate reflector parts View.v as itwere, the filament body in an oblique direction so that the V isshortened with a smaller .apex;.than.the.virtualone. Such reflectorparts produce, for example, aseriesof images 26,. l

The better light distribution ensured by the use of a lamp according tothe inventioni's illustrated- Fig. 14-. The 1 diagram shows 'themeasuring resultsof the illumination intensity on ascreen arranged atrightangles to the axis of this beamlight and at ajistance of, ill n. infront'l l etbof. The distances" 'Qve and; below thefaxi areindicated' mc The 'beamligh't is arranged at the height of'l m. The light strikingthe screen 20 cms. below would strike the road at a distance of 50 m. infront of the vehicle, and the light striking the screen 80 cms. below 0would strike the road at a distance of 12.5 m. in front of the vehicle.

The full line 21 indicates the illumination obtained with the use of alamp hitherto employed, in which the straight "dipping filament extendsjust above the optical axis (wire 3 shown in Figs. 1 and 2), whereas thebroken line 28 indicates the illumination obtained with the use of aV-shaped dipping filament according to the invention (the wire 3 shownin Figs. 11 and 12). As appears from the points of intersection with thelines 29 and 30, which indicate the illumination intensity at distancesof 50 and 12.5 m. respectively in front of the vehicle on the road, theformer has become twice as high and the latter has decreased to onehalf.

The beam pattern shown in Fig. and the diagram shown in Fig. 4 areobtained with the use of V-shaped filaments, the lengths of the limbsbeing equal. If the length of one of the limbs is increased relativelyto that of the other, the diameter of the beam pattern again increases.This increase is generally undesirable, but in view of the fact that theradius of the beam pattern in one direction increases more than in theother, it may in some circumstances be an advantage to use anasymmetrical v, for example ii. it is desired to direct a stronger lightflux to one side of the road. The beam pattern produced by such a lampis shown in Fig. 15. The reflector parts located in or near the verticalplane through the axis produce a series of images 24' of the filamenttwo of which are shown. The reflector parts extending in or near thehorizontal plane through the axis produce two series of images 25' and25" which are asymmetrical, similarly to the filament. The reflectorparts extending in oblique planes through the axis produced series ofimage '26 and 26". From the figure it appears that the verticaldiffusion is still smaller than that of a suitable filament (Fig. 3),and show that an improvement in luminous intensity is obtained closebelow the horizontal outline of the beam.

The methods of construction of a lamp according to the invention neednot depart considerably from the methods used for known lamps comprisinga dipping filament. In the latter, one end of the straight filament isusually welded to the screen, while the other end is secured to aterminal wire. The V-shaped filament in the lamp according to theinvention may be suspended in the same manner, as shown in Fig. 15.

The scr ee'rrd isi securedi-zat one. side ;,tO. a; supply. conductor -3I and:- thev shapedi-i filament 35. is. suspended between one oi theedgesof the' screen and a. second:supply.condi1ctor...13-22- The shapeof the screen ismatched to that; ofethe filament, so .that i the edges.1 3:;and I35: extenclz-p'arallell; to the-limbs ofithewirelx A; lfurtheri construction is, shown in: Figs. 18'; IQ -andeZOl 'Ihe ends:ofzthe filament 3..areeach secured to a supply conductor 3t: and-132arespec.-. tively; This'apermitsz morelfreedom in. the farrangementofsthese ends .than .in. the. constructtionslshown in:.1 'igs.. 16 and I7,-in which oneend invariablyllies. on. :edge of I the-.screen. (At thisenda staywire could-, oficourse, be .welded to the screen, but. then: anadditional element x is 1'62- quiredJ- v Inuthe-iconstruction shown: inFigs. -18 1:0 20 the screen his: provided at' the rear side and the top.with. a. groove or. indent: which 'is prolonged about the edge formed bythe transition of these sides. The stay wire 3| is secured by welding inthis groove. In this way the position of the screen is fixedunequivocally prior to the welding operation.

In the construction shown in Fig. 21, the filament body comprises twoparallel filaments 3' and 3". The top of the V is connected to thesupply conductor 32, the free ends to the screen 4. The screen is againprovided with a groove, in which the bent end of the supply conductor 3|is secured.

Such a construction has the advantage that the burning out of one of thelimbs of the filament results only in a decrease in light output of thelamp but not in its extinction.

In order to relieve the filament as much as possible of mechanical loadsdue to vibration of the filament joints, particularly since the supplyconductor supporting the screen will vibrate with a frequency andamplitude differing from those of the other supply conductor, it isadvisable to provide an insulating, mechanical joint between the ends ofthese supply conductors, for example in the manner shown in Figs. 1'7and 18, where a stay rod 33 is welded to one supply conductor 32 and astay rod 34 is welded in the screen 4. The two rods are connectedtogether by means of an insulating glass bead 35. This construction,which is known per se (for example British patent specification 393,886)may, of course, also be used in the lamps shown in Figs. 18 to 21.

What I claim is:

1. An incandescent lamp for use with a reflector having an optical axiscomprising a bulb, a main filament near the focal point of saidreflector, a cup-shaped screen within said bulb, a V-shaped filamentlocated between two lateral edges of said screen, each of said mainfilament, said V-shaped filament and said optical axis lying in the sameplane, said V-shaped filament having its apex pointing toward said mainfilament and the angle between one of the limbs of the V-shaped filamentand the optical axis on the side of the V-shaped filament facing awayfrom the reflector being between 15 and 60.

2. An incandescent lamp for use with a reflector having an optical axiscomprising a bulb, a cap for said bulb, the axis of said cap beingcoincident with the optical axis of said reflector, a main filament, acup-shaped screen within said bulb, a V-shaped filament located betweentwo lateral edges of said screen, each of said main filament, saidV-shaped filament and said cap axis lying in the same plane, saidV-shaped fila- 7 ment having its apex pointing toward said main filamentand the angle between one of the limbs of the V-shaped filament and theaxis of the cap on the side of the V-shaped filament facing away fromthe refiector being between 15 and 60.

3. An incandescent lamp for use with a reflector having an optical axiscomprising a bulb, a cap for said bulb, the axis of said cap beingcoincident with the optical axis of said reflector, a main filamentlocated at the focal point of said reflector, a cup-shaped screen withinsaid bulb on the side of said main filament remote from said reflector,a V-shaped filament located between two lateral edges of said screen,each of said main filament, said V-shaped filament, said lateral edgesand said axis lying in the same plane, said V-shaped filament having itsapex pointing toward said main filament and the angle between one of thelimbs of the V-shaped filament and 8 the axis of the cap on the side ofthe V-shaped filament facing away from the reflector being between 15"and 60.

JOHANNES RIJNDERS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,071,979 Honing Feb. 23, 1937FOREIGN PATENTS Number Country Date 481,910 Great Britain Mar. 21, 1938666,004 Germany July 19, 1936 822,808 France Sept. 27, 1937

